lol/log.go

// Package lol (log of location) is a simple logging library that prints a high
// precision unix timestamp and the source location of a log print to make
// tracing errors simpler. Includes a set of logging levels and the ability to
// filter out higher log levels for a more quiet output.
package lol

import (
	"fmt"
	"io"
	"os"
	"runtime"
	"sync/atomic"
	"time"

	"github.com/davecgh/go-spew/spew"
)

const (
	Off = iota
	Fatal
	Error
	Warn
	Info
	Debug
	Trace
)

var LevelNames = []string{
	"off",
	"fatal",
	"error",
	"warn",
	"info",
	"debug",
	"trace",
}

type (
	// LevelPrinter defines a set of terminal printing primitives that output
	// with extra data, time, log logLevelList, and code location

	// Ln prints lists of server with spaces in between
	Ln func(a ...interface{})
	// F prints like fmt.Println surrounded []byte log details
	F func(format string, a ...interface{})
	// S prints a spew.Sdump for an enveloper slice
	S func(a ...interface{})
	// C accepts a function so that the extra computation can be avoided if it is not being
	// viewed
	C func(closure func() string)
	// Chk is a shortcut for printing if there is an error, or returning true
	Chk func(e error) bool
	// Err is a pass-through function that uses fmt.Errorf to construct an error and returns the
	// error after printing it to the log
	Err func(format string, a ...any) error

	// LevelPrinter is the set of log printers on each log level.
	LevelPrinter struct {
		Ln
		F
		S
		C
		Chk
		Err
	}

	// LevelSpec is the name, ID and Colorizer for a log level.
	LevelSpec struct {
		ID        int
		Name      string
		Colorizer func(a ...any) string
	}

	// Entry is a log entry to be printed as json to the log file
	Entry struct {
		Time         time.Time
		Level        string
		Package      string
		CodeLocation string
		Text         string
	}
)

var (
	// Writer can be swapped out for any io.*Writer* that you want to use instead of stdout.
	Writer io.Writer = os.Stderr

	// LevelSpecs specifies the id, string name and color-printing function
	LevelSpecs = []LevelSpec{
		{Off, " ", NoSprint},
		{Fatal, "☠️ ", fmt.Sprint},
		{Error, "🚨 ", fmt.Sprint},
		{Warn, "⚠️ ", fmt.Sprint},
		{Info, "ℹ️ ", fmt.Sprint},
		{Debug, "🔎 ", fmt.Sprint},
		{Trace, "👻 ", fmt.Sprint},
	}
)

// NoSprint is a noop for sprint (it returns nothing no matter what is given to it).
func NoSprint(_ ...any) string { return "" }

// Log is a set of log printers for the various Level items.
type Log struct {
	F, E, W, I, D, T LevelPrinter
}

// Check is the set of log levels for a Check operation (prints an error if the error is not
// nil).
type Check struct {
	F, E, W, I, D, T Chk
}

// Errorf prints an error that is also returned as an error, so the error is logged at the site.
type Errorf struct {
	F, E, W, I, D, T Err
}

// Logger is a collection of things that creates a logger, including levels.
type Logger struct {
	*Log
	*Check
	*Errorf
}

// Level is the level that the logger is printing at.
var Level atomic.Int32

// Main is the main logger.
var Main = &Logger{}

func init() {
	// Main = &Logger{}
	Main.Log, Main.Check, Main.Errorf = New(os.Stderr, 2)
	ll := os.Getenv("LOG_LEVEL")
	if ll == "" {
		SetLogLevel("info")
	} else {
		for i := range LevelNames {
			if ll == LevelNames[i] {
				SetLoggers(i)
				return
			}
		}
		SetLoggers(Info)
	}
}

// SetLoggers configures a log level.
func SetLoggers(level int) {
	Main.Log.T.F("log level %s", LevelSpecs[level].Colorizer(LevelNames[level]))
	Level.Store(int32(level))
}

// GetLogLevel returns the log level number of a string log level.
func GetLogLevel(level string) (i int) {
	for i = range LevelNames {
		if level == LevelNames[i] {
			return i
		}
	}
	return Info
}

// SetLogLevel sets the log level of the logger.
func SetLogLevel(level string) {
	for i := range LevelNames {
		if level == LevelNames[i] {
			SetLoggers(i)
			return
		}
	}
	SetLoggers(Trace)
}

// JoinStrings joins together anything into a set of strings with space separating the items.
func JoinStrings(a ...any) (s string) {
	for i := range a {
		s += fmt.Sprint(a[i])
		if i < len(a)-1 {
			s += " "
		}
	}
	return
}

var msgCol = fmt.Sprint

// GetPrinter returns a full logger that writes to the provided io.Writer.
func GetPrinter(l int32, writer io.Writer, skip int) LevelPrinter {
	return LevelPrinter{
		Ln: func(a ...interface{}) {
			if Level.Load() < l {
				return
			}
			_, _ = fmt.Fprintf(
				writer,
				"%s%s%s %s\n",
				msgCol(TimeStamper()),
				LevelSpecs[l].Colorizer(LevelSpecs[l].Name),
				JoinStrings(a...),
				msgCol(GetLoc(skip)),
			)
		},
		F: func(format string, a ...interface{}) {
			if Level.Load() < l {
				return
			}
			_, _ = fmt.Fprintf(
				writer,
				"%s%s%s %s\n",
				msgCol(TimeStamper()),
				LevelSpecs[l].Colorizer(LevelSpecs[l].Name),
				fmt.Sprintf(format, a...),
				msgCol(GetLoc(skip)),
			)
		},
		S: func(a ...interface{}) {
			if Level.Load() < l {
				return
			}
			_, _ = fmt.Fprintf(
				writer,
				"%s%s%s %s\n",
				msgCol(TimeStamper()),
				LevelSpecs[l].Colorizer(LevelSpecs[l].Name),
				spew.Sdump(a...),
				msgCol(GetLoc(skip)),
			)
		},
		C: func(closure func() string) {
			if Level.Load() < l {
				return
			}
			_, _ = fmt.Fprintf(
				writer,
				"%s%s%s %s\n",
				msgCol(TimeStamper()),
				LevelSpecs[l].Colorizer(LevelSpecs[l].Name),
				closure(),
				msgCol(GetLoc(skip)),
			)
		},
		Chk: func(e error) bool {
			if Level.Load() < l {
				return e != nil
			}
			if e != nil {
				_, _ = fmt.Fprintf(
					writer,
					"%s%s%s %s\n",
					msgCol(TimeStamper()),
					LevelSpecs[l].Colorizer(LevelSpecs[l].Name),
					e.Error(),
					msgCol(GetLoc(skip)),
				)
				return true
			}
			return false
		},
		Err: func(format string, a ...interface{}) error {
			if Level.Load() >= l {
				_, _ = fmt.Fprintf(
					writer,
					"%s%s%s %s\n",
					msgCol(TimeStamper()),
					LevelSpecs[l].Colorizer(LevelSpecs[l].Name),
					fmt.Sprintf(format, a...),
					msgCol(GetLoc(skip)),
				)
			}
			return fmt.Errorf(format, a...)
		},
	}
}

// GetNullPrinter is a logger that doesn't log.
func GetNullPrinter() LevelPrinter {
	return LevelPrinter{
		Ln:  func(a ...interface{}) {},
		F:   func(format string, a ...interface{}) {},
		S:   func(a ...interface{}) {},
		C:   func(closure func() string) {},
		Chk: func(e error) bool { return e != nil },
		Err: func(
			format string, a ...interface{},
		) error {
			return fmt.Errorf(format, a...)
		},
	}
}

// New creates a new logger with all the levels and things.
func New(writer io.Writer, skip int) (l *Log, c *Check, errorf *Errorf) {
	if writer == nil {
		writer = Writer
	}
	l = &Log{
		T: GetPrinter(Trace, writer, skip),
		D: GetPrinter(Debug, writer, skip),
		I: GetPrinter(Info, writer, skip),
		W: GetPrinter(Warn, writer, skip),
		E: GetPrinter(Error, writer, skip),
		F: GetPrinter(Fatal, writer, skip),
	}
	c = &Check{
		F: l.F.Chk,
		E: l.E.Chk,
		W: l.W.Chk,
		I: l.I.Chk,
		D: l.D.Chk,
		T: l.T.Chk,
	}
	errorf = &Errorf{
		F: l.F.Err,
		E: l.E.Err,
		W: l.W.Err,
		I: l.I.Err,
		D: l.D.Err,
		T: l.T.Err,
	}
	return
}

// TimeStamper generates the timestamp for logs.
func TimeStamper() (s string) {
	s = fmt.Sprint(time.Now().UnixMicro())
	return
}

// GetLoc returns the code location of the caller.
func GetLoc(skip int) (output string) {
	_, file, line, _ := runtime.Caller(skip)
	output = fmt.Sprintf("%s:%d", file, line)
	return
}